1. Field of the Invention
The present invention relates to a method for manufacturing an ink jet head for forming liquid droplets by discharging recording liquid by utilizing an ink jet recording technique, and more particularly, it relates to a method and apparatus for bonding a top member to a base member via wall members for defining ink passages therein, in the manufacture of a plurality of ink jet heads collectively.
2. Related Background Art
As shown in FIG. 4, in an ink jet head used with ink jet recording systems (liquid jet recording systems), a base member is formed by arranging a predetermined number (three in FIG. 4) of energy generators (for example, electrothermal conversion members) 32 for generating energy used to discharge ink on a support plate 31 made of silicon and the like, and a pattern corresponding to discharge openings 33, ink passages 34 and a common ink chamber 35 is formed by the lithographic technique to obtain such discharge openings, ink passages and ink chamber, and a top member 36 is covered on the formed pattern, thus manufacturing the ink jet head. Conventionally, in order to bond the top member 36 to the base member, an adhesive capable of being softened by the illumination of ultraviolet ray (UV) was coated on one surface of the top member 36, the top member was positioned with respect to the base member on which the pattern was formed, the top and base members were abutted against each other with an appropriate pressure, and then the adhesive was cured by illuminating the ultraviolet ray thereon, thus adhering both members to each other. The pressure for bonding these members to each other can be obtained by rollers (FIG. 5) or a press for applying the pressure to the parallel members (FIG. 6).
In the case where the pressure is obtained by the rollers, as shown in FIG. 5, the top member 36 and the base member 43 with the interposition of wall members 42 defining ink passages communicating with discharge openings are passed between and pressed by pressure rollers 41, 41' rotated in directions shown by the arrows A. Incidentally, the reference numeral 45 denotes an adhesive layer for adhering the wall members 42 to the top member 36; and 46 denotes a work support on which the base member 43 and the top member 36 are rested and which can be used at need.
When such rollers are used to pressurize the members against each other, it is feared that the following problems arise:
(1) When the base member and the top member (which constitutes a "work") positioned with respect to each other are inserted between the rollers, if one of the members is contacted with the roller, the discrepancy in the relative position between the base member and the top member will occur. PA1 (2) If hard rollers are used, the penetrating amount of the wall members into the adhesive layer will be non-uniform or uneven due to the dispersion in the thickness accuracy of the work and/or work support, which results in the dispersion in positions of the discharge openings in height direction. Thus, the dimensions of the discharge openings do not become constant or uniform. Further, if any hard foreign matter exists between the adhesive layer and the wall member and/or top member, the dispersion in the dimensions of the discharge openings will be further increased. PA1 (3) If the rollers covered by soft rubber layers are used, since the surfaces of the rollers are soft, as shown in FIG. 7, the dispersion (as shown X, Y in FIG. 7) in the penetrating amount of the wall members 42 into the adhesive layer 45 will occur due to the deformation of the rollers, with the result that the dimensions of the discharge openings do not become constant or uniform. PA1 (4) Due to the dispersion in the thickness accuracy of the work and/or work support 46, unevenness in the press surfaces, and/or unparallelism between the upper and lower surfaces of the press, the same problem as mentioned in the above Item (2) occurs. PA1 (5) If an elastic flat plate 49 is interposed between the pressure member 48 and the top member 36, as shown in FIG. 8, since the pressure value per a unit area is varied between regions where there are greater portions (wall members and the like) to be adhered and regions where there are less portions to be adhered, the dispersion in the penetrating amount into the adhesive layer will occur, with the result that the dimensions of the discharge openings do not become constant or uniform. PA1 (6) If the parallelism of the press is insufficient, since the pressure member of the press initially contacts with the top member locally, the relative position between the top member and the base member will be changed during the operation of the press. PA1 (a) The top member is temporarily adhered to the base member at plural peripheral points thereof with a two liquid component instantaneous adhesive in order to prevent the discrepancy in the relative position between the top and base members in subsequent processes or steps after they are bonded together. PA1 (b) A heating/cooling means is provided in a press, so that the adhesive is heated during the bonding to reduce the viscosity of the adhesive, thereby facilitating the bonding between the top member and the base member and that the adhesive is cooled after the bonding to increase the viscosity of the adhesive, thereby effectively preventing the camber of the member(s) due to the difference in the coefficient of thermal expansion between the members and the resulting separation therebetween. PA1 (c) Recessed portions corresponding to the wall members defining the ink passages and wall portions defining common ink chambers are formed in a pressure member of the press so that only the wall members and the wall portions are pressurized by the press during the bonding between the top member and the base member. That is to say, if there is no such recessed portions, thinner wall portions of the top member directly opposing the ink chambers are also pressurized by the pressure member, with the result that the top member is distorted as shown in FIG. 9. The distortion of the top member will cause the difference in the penetrating amount of the wall members defining the ink passages and the wall portions defining the ink chambers into the adhesive. Further, by interposing a thin elastic layer such as a rubber layer between the work and the pressure member of the press, the uneven pressure generated due to the dispersion in the thickness of the work and the pressure member and/or the parallelism between the work and the pressure member and acting on the work can be compensated. PA1 (d) In order to prevent the top member and the base member from distorting after the bonding therebetween, the work is cooled by the above-mentioned cooling means while they are being pressurized after adhesion, thus releasing the stress due to the thermal expansion of the members. Thereafter, the adhesive layer is cured by illuminating the ultraviolet rays thereon. To this end, the pressure member and at least one of the base member and the top member are made of UV permeable material.
On the other hand, when the press is used to pressurize the members against each other by pressing the work rested on a press platform 47 by a pressure member 48 as shown in FIG. 6, it is feared that the following problems arise:
Further, after the adhesion, the adhered work is dismounted from the press and the adhesive layer is cured. In this case, it is feared that the adhesive layer is separated unless the temperature of the adhesive is lowered to a room temperature level to increase the viscosity of the adhesive during the dismounting of the work and the ultraviolet rays are illuminated onto the adhesive layer immediately after the dismounting of the work, because, due to the fact that the viscosity of the adhesive is reduced to facilitate the adhesion by increasing the temperature during the adhesion process, if the coefficient of thermal expansion of the base member (for example, made of silicone wafer) differs from that of the top member (for example, made of glass), the camber will occur during the cooling of the members, thus causing the separation of the adhesive layer.